Disposable diapers have met with increasing commercial acceptance in recent years, primarily because of their convenience. Such diapers have conventionally included a facing layer to be brought into contact with an infant's skin, an absorbent panel adjacent thereto, and a water-impervious or a water repellent outer layer.
Known types of disposable diapers have had many functional deficiencies including inadequate absorptive capacity and inability to keep moisture away from the surface of the diaper which comes into contact with the infant's skin. Another serious drawback of prior art diapers is the tendency for liquid to leak around the edges of the diaper, particularly at night during periods of heavy discharge.
A significant advance in the art is provided by the diaper constructions disclosed and claimed in commonly assigned, Mesek et al., U.S. Pat. No. 3,612,055. The diaper structure illustrated therein includes, in order; a fibrous facing layer which is to be brought into contact with the infant's skin; an absorbent panel comprising a batt of highly porous, loosely compacted cellulose fibers having a paper-like, densified, highly compacted cellulosic fibrous layer integral with the loosely compacted batt; and an impervious backing sheet adhered to the densified layer portion of the batt throughout the interface therebetween. The facing layer is of porous construction and its fibers have less wettability for water than the fibers of the loosely compacted batt, resulting in a tendency for liquid to flow from the facing web into the batt. The densified fibrous layer has a smaller average pore size than the loosely compacted batt resulting in a tendency for liquid to flow from the batt into the densified layer.
In one embodiment of the diaper disclosed in the above mentioned patent, having particular utility during periods of heavy discharge, the absorbent panel of the diaper includes a relatively small second batt, similar to the batt already named, superimposed on the larger first named batt. This construction not only provides an increased absorptive capacity for the diaper, but also provides for greater compressibility at the center of the diaper because of the increased batt thickness. When the batt portion of the diaper is compressed by the infant's weight, the distances between adjacent fibers is decreased, i.e., there is a smaller effective capillary radius between adjacent fibers, particularly in the center section of the batt portion of the diaper. In consequence of this, there is a greater wickability at the more highly compressed center portion of the batt as compared to the less compressed marginal portions. This latter construction tends to keep liquid in place in the center portion of the diaper, and prevents it from leaking around the edges thereof.
In the last mentioned diaper embodiment, the integral densified layer portion of the larger batt is in face-to-face engagement with the backing sheet, thus helping the urine to spread laterally throughout the length and width of the batt beyond the edges of the smaller batt. The rapid spread of the urine by means of the densified layer is desirable, but carrying the liquid to the peripheral edges of the larger batt increases the likelihood of leakage at the edges of the diaper.
An improvement in multi-layer batt diapers is disclosed in commonly assigned copending, Mesek Application Ser. No. 187,248. The diaper structure utilized therein includes an absorbent panel consisting of two differently sized, superposed batt layers of highly porous, loosely compacted cellulose fibers, sandwiched between a porous facing layer and a water-impervious sheet, with the smaller of the batt layers being positioned adjacent the backing sheet, and with the larger batt layer being positioned over the smaller batt layer.
In this last mentioned embodiment, the added thickness provided by the smaller batt effectively confines large volume discharge of urine in areas out of contact with the infant's skin. However, due to the two-piece construction of the batt portions of this diaper, a large amount of cellulose fibers must be used, and this embodiment requires complex production apparatus to provide proper cutting and positioning of the two batts in registry with one another and the other components of the diaper.